In the 4000 series these 1 1/2 in Stainless Steel Thumb Screws are located on the A/C cover plate. Featuring a knurled round knob, this thumb screw allows for easy, tool-free adjustments, making it ideal for situations where quick and frequent changes are necessary. The stainless-steel construction ensures excellent corrosion resistance, making it suitable for both indoor and outdoor use. This bag of hardware is great to have on hand in case you need a quick replacement, or a screw gets misplaced when changing your A/C filter.